316 Miscellaneous. 



down the tube towards the point of exit. He finds that throughout 

 the organic axis of the ovum is parallel to the axis of the body 

 of the parent, and, further, that the pole of the ovum which is 

 directed towards the narrow part of the ovigerous tube, i. e. towards 

 the head of the mother, is the cephalic pole of the ovum. The 

 maturation of the ova goes on approximately pari passu in all 

 the tubes, so that at a given moment each tube presents a mature 

 ovum placed close to the calyx or oviduct, and oviposition and the 

 formation of the cocoon are then imminent. He describes the 

 latter process as follows : — 



" The serific glands, as Leon Dufour calls them, form at this period 

 a voluminous bundle ventrally situated and composed of very long 

 tubes, coiled together, bifid and naultifid. These tubes are filled with an 

 opaque, readily coagulable substance, in which are disseminated an 

 infinite number of crystals. They are prisms with a rhombic base, 

 presenting a small rectangular facet of truncature in place of the pro- 

 jecting edges. They measure, on the average, 15 /i, are insoluble 

 in water and in weak nitric acid; they are, on the contrary, 

 destroyed without any disengagement of gas by concentrated sulphuric 

 acid ; and caustic potash dissolves them still more rapidly. These 

 crystals are destined to the construction of the cocoon, which is 

 formed by an assemblage of these crystals cemented by the coagu- 

 lated substance in the midst of which they have originated. 



" This cocoon, which Leon Dufour compares to a small, closed 

 valise, is ovoid and presents a denticulated crest which is the line of 

 dehiscence. The posterior extremity (that which issues first at the 

 moment of delivery) is generally a little the thicker ; the other is 

 easily recognizable owing to the presence of a sort of small hilum. 

 The line of dehiscence is superior, consequently corresponding to the 

 dorsal surface of the insect. The eggs, sixteen in number, are 

 arranged in two rows vertically in this cocoon ; finally, in more 

 than 100 cocoons that I have examined I have always found the 

 heads of all the embryos directed towards the line of dehiscence. 



" I have had the opportunity of observing directly the fabrication 

 of the cocoon and the arrangement of the eggs in its interior. The 

 two oviducts debouch a little in front of the subgenital plate at the 



superior level of the genital armature which is essentially 



formed of two episternites and of a sternite with two biramose branches. 

 The whole forms a sort of funnel or speculum with four mobile 

 branches, and placed obliquely from in front backwards, and from 

 above downwards. The egg coming from the oviduct falls into this 

 funnel, which seizes it and places it side by side with those previously 

 laid ; at the same time, by the combined mechanism of the walls of 

 the genital sac and the pieces of the armature, the coagulable matter 

 and its crystals are uniformly spread and take the form of the 

 cocoon. The line of dehiscence is produced by a pressure exerted 

 by the superior part of the sternite and perhaps also by the groove of 

 the tergite of the anal segment. The cocoon is moreover supported 

 beneath by the subgenital plates.'' 



The egg always falls into the genital armature with the caudal 

 pole downwards. — Compies Eendns, August 10, 1885, p. 444. 



